Challenges in material specification for concrete …...AS 2758.1:2014 AS 2558 is called up by AS...
Transcript of Challenges in material specification for concrete …...AS 2758.1:2014 AS 2558 is called up by AS...
Challenges in material specification for
concrete performance
A consultant’s view
John Figueroa
24 & 30 July 2018
Durability Requirements and Design Standards
AS 3600-2009 AS 5100-2009
DESIGN LIFE OF CONCRETE STRUCTURES
Guides to Pavement
Technology
DESIGN LIFE (YEARS)
RE
QU
IRE
ME
NT
S
Current Trend (Challenge)
Specification and Supply of Concrete
This Standard sets out the minimum requirements for:
(a) the materials, plant and equipment used in the supply of
concrete;
(b) the production and, if applicable, the delivery of concrete in the
plastic state;
(c) specifying, sampling, testing and compliance with specified
properties of plastic and hardened concrete; and
(d) the uniformity of mixing.
AS 1379-2007 (R2017)
Concrete aggregates
AS 2758.1:2014
AS 2558 is called up by AS 3600, Concrete structures. In this
Standard, extensive reference is made to AS 1141, Methods for
sampling and testing aggregates (series), which is designed to
include all aggregate tests, not only those for concrete.
General purpose and blended cements
AS 3972—2010
Due to the Global warming effect the Australian Government has
initiated programs to reduce Australia’s carbon emissions. Portland
cement is recognised as an energy intensive material and the aim
is to reduce its environmental effect in terms of reducing
greenhouse gas emissions.
SR
SL
GP
SL / GP
+ SCM
Supplementary Cementitious Material
(SCM)
AS 3582.1:2016
Fly ash replacements beyond 35% are problematical, high
replacement levels of fly ash lead to significantly lower rates of
strength gain in the concrete and significantly increase the curing
time required to achieve durable concrete.
Fly Ash
Although most fly ash spheres are solid, some particles, called cenospheres,are hollow
Source: Design and Control of Concrete Mixtures EB001, PCA (2016)
SCM – Ground granulated blast
furnace slag
AS 3582.2:2016
Non-metallic molten material (slag) obtained from the waste stream
of iron ore blast furnace. Glassy granulated material.
Granules are ground to a suitable fineness (generally finer than
Portland cement). It can be used in concrete mixtures to enhance
strength, durability and sustainability.
SCM – Amorphous silica
AS 3582.3:2014
The most benefit is obtained in Exposure Class C conditions or
where concrete is directly exposed to chlorides or other aggressive
environments. Silica fume should not generally be used at a
replacement level greater than 10%.
Typically used in high performance concrete
Construction Specifications
for Concrete in NSW
BRIDGES SHOTCRETE
SUBBASE BASE GENERAL WORK
B80 -Range of SCM Limits
Range of SCM Limits (B82 & R68)
Range of SCM Limits (R82)
Range of SCM Limits (R83)
Durability Requirements
Chemical Attack on Concrete
Corrosion of reinforcement by
(a) Chloride ingress
(b) Carbonation
Sulphate Attack
Sea water attack
Acid attack
Delayed ettringite formation
Alkali aggregate reaction
Alkali carbonate reaction
Freezing and thawing related damage
Need to reduce
permeation
mechanisms
Permeability
Absorption
Diffusion
Material Standard Title
Concrete
DBV, 2001
German Society for Concrete and
Construction Technology (superseded)
Steel Fibre Concrete [DBV-
Guide to Good Practice]
BS EN 14889-1, 2006
British Standards Institution,
EuroCode
Fibres for Concrete.
Steel Fibres. Definition,
specifications and conformity
DAfStb, 2015
German Committee for Reinforced
Concrete
Commentary on the DAfStb
Guideline
Steel fibre reinforced concrete
ASTM A820, 2016
American Society for Testing and
Materials
Specification for Steel Fibres
for Fibre Reinforced Concrete
Shotcrete CS, 2007
UK Concrete Society
TR 63 Guidance for the
design of steel-fibre-
reinforced concrete (includes
amendment No. 1 Oct 2007)
Concrete Standards for Shotcrete
Source: Bertuzzi (2017)
Shotcrete Evolution
Source: Australian Shotcrete Society
Tunnel Project in NSW
Shotcrete with
steel fibre
Concrete cast in situ
Lean Concrete Subbase
CRCP (not
built yet)
Shrinkage Limits
AS 1379
1,000 microstrain
The default values
in AS 5100 are:
800 microstrain for
Sydney and
Brisbane,
900 microstrain for
Melbourne and
1000 microstrain
elsewhere.
AS 5100 Section 16
‘Steel fibre reinforced concrete’
EN 14651:2005
Concrete Roundabout Pavements in NSW
Approaching 40 years of construction (fixed-formed) experience
Introduced with a fibre
content of 1% or 75 kg/m3
Reduced to 55 kg/m3
depending on ultimate
tensile strength, aspect
ratio and hardness pf
fibres
Maintenance of Concrete Pavement Roundabouts
Diamond Grinding after 25 - 30 years of service
SFRC in Industrial Floors
AS 5100-2017
Industry
Guides before
AS 5100 -2017
Typical dosage rates
20 – 40 kg/m3
ASTM C1550 - 10
Flexural Toughness
Alternative Design Methods and Materials
AS 5100 does not preclude the use of
techniques or materials other than those
specified in AS 5100.
Source: Hilton (2014)
Use of Synthetic Fibres in Concrete
Macro SyntheticMicro Synthetic
May provide additional structural
strength in concrete elements or
shotcrete
Used for plastic shrinkage control,
improved abrasion resistance and
passive fire protection
Refer to Concrete Society TR65
Short-Slab PCP over unbound subbase
US Study on Thin Concrete Overlays Over 90% of all fibre reinforced overlays in the USA were constructed with
structural synthetic fibres.
Macro synthetic fibres do not significantly improve the compressive strength,
modulus of elasticity and modulus of rupture of concrete.
The residual strength of structural FRC is improved with macro synthetic
fibres
Dosage of 3.5 - 5.0 kg/m3 to improve early-age strength of concrete
The geometry, length, aspect ratio and stiffness of synthetic fibres have a
significant influence in improving post-crack properties of concrete. Crimped,
embossed, or twisted fibres showed better performance than straight
synthetic fibres.Traditional design
Short-slab design
Design Philosophy in AS 5100
Design must consider:
Intended function
Aesthetics
Constructability
Maintainability
Sustainability
Climate change
Safety in design
AS 5100 Clause 8.3 Limit states
Cl 8.3.1 All ultimate design actions are now defined
as actions which have a 5% probability of being
exceeded during the design life. For a design life of
100 years this represents a return interval of 2000
years.
AS 5100 Section 10 Sustainability
“Social” sustainability
Does the structure as constructed effectively fulfil its functional intention?
“Economic” sustainability
Is the structure as constructed, cost effective over its full life cycle?
“Environmental” sustainability
Does the structure, as constructed, provide unnecessary harm to the environment?
Social Sustainability
Is the structure in the right location?
Does it most effectively draw communities together?
Does it enhance the safety and security of people?
Does it promote and encourage equity and diversity?
Does it promote wellbeing by being developed froman understanding of what people need from placeswhere they live and work?
Is the structure safe to construct and maintain?
Economic Sustainability
Is the cost of the structure the most cost effective?
Is the anticipated maintenance costs of the structureminimal?
Is the design life of the bridge commensurate with itsintended function?
Will the structure require widening, strengthening, lengthening in the future and thus require an unnecessary expense compared to undertaking this work now?
Is the form and function of the structure sufficiently robustthat the designated design life is expected to be achieved?
Does the construction and maintenance of the structureunnecessarily deplete non-renewable resources?
Does the design or function affect the future economic valueof natural resources?
Does the design provide optimal economic value?
Environmental Sustainability
Material Embodied
energy
(GJ/tonne)
Aluminium 155
Bitumen 47
Brick 3
Concrete (100% cement) 1.2
Concrete (25% fly ash) 1.0
Paint 68
Reinf concrete (25% fly ash) 2.3
Rubber 102
Steel 24
Stone 0.1
Timber 8
Does the structure, as constructed, provide unnecessary
harm to the environment?
Industry Initiatives to reduce Carbon Emissions
Source: BZE (2017)
Bluey TechnologiesBLUCEM FSC BINDER
Calcium Sulfoaluminate (CSA) Cement
Source:
Unconfined Compressive Strength
Water: Cement 0.20 0.25
Concrete Runways
Source: http://www.nycaviation.com/2015/01/built-last-runways-
built/37734
Brisbane West Wellcamp Airport
EFC Geopolymer Concrete, supplied and
paved by Wagners (2014)Source: http://www.quarrymagazine.com/Article/6675/Can-do-attitude-proves-the-difference-in-airport-project
Technology Transfer
Professor Dan
Zollinger
Texas A&M University
1993
O'Hare International Airport in Chicago, 9L - 27R
L: 2.4 km
W: 45 m
T: 400 mm
Workability test for slip-formed concrete pavements
Improvements in Mix Design
Source: Ley (2012)
Workability test for slip-formed concrete pavements
Tarantula Curve
Improving Concrete Durability and
Sustainability Using Internal Curing
Curing is one of seven essential procedures “that make concrete
capable of providing decades of service with little or no
maintenance.” [ACI 201 2R-08, Guide to Durable Concrete]
ACI: Internal Curing: “supplying water throughout a freshly placed
cementitious mixture using reservoirs, via pre-wetted lightweight
aggregates, that readily release water as needed for hydration or to replace
moisture lost through evaporation or self- desiccation ”
Source: FHWA Tech Brief (2016)
What is Light Weight Aggregate
Expanded shale, clay andslate (ESCS)
Structural, ceramic aggregate produced in a rotary kiln
Less than half the unit weight of ordinary aggregate
Complies with ASTM C-330
and C-331
Mixture Design for IC Concrete
Same method to that of conventional concrete. A portion of the conventional fine
aggregate is replaced with a prewetted lightweight fine aggregate.
Example:
Source: FHWA Tech Brief (2016)
Plain Concrete0.6 mm wide crack
observed @ 12 days
IC Concrete0.4 mm wide crack
observed @ 43 days
Large Scale Testing at Purdue University
Source: Schlitter (2010)
Test Slabs 4.5m long with end restraint. 0.30 w/c Curing: 2 days sealed, then 230 C @ 50% RH
Benefits of using internal curing
Less shrinkage, less cracking
More hydration & SCM reaction
Improved durability by
Lower water absorption
Lower chloride permeability & penetration
Longer service life
Less life cycle costs
Increased sustainability
Technology Updates – Concrete Paving
Pavement Replacement System
Mix Design Approved by RMS
Triple Roller Tube Paver
Motorway Project in
Sydney
Slab Replacement Work in Sydney
Conclusions
Australian Standards
Established specifications (e.g. RMS) with project-specific
amendments
Specification choices to achieve the design life
Project amendments are generally required to allow the
introduction of new technology and achieve improved
durability and sustainability requirements.
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